OP, it's really important to be clear, as others have said, about which of your fears and unfounded and which are more grounded, eg. Yr 2 sats are quite generally nothing to be concerned about. Lining up to go into class is just health and safety common sense as well as good manners. Most of reception and now lots of yr 1is very play based and child-led.
Others of your concerns (children's behaviour/your child not being challenged) might be more valid but, again, are all based on worst-case scenarios.
I speak as someone who would have home educated at the drop of a hat for my August born, AS son, but I decided to work out what my worst fears about schooling were and address just those. For me, they were- staff not fully understanding his specific needs and the unnatural (as I see it) separation of children into narrow age bands based on their birthdays.
So I actively sought out a very small school for him where all the staff knew all the children intimately and where reception children played with year 6s and everyone in between. Of course there were a few niggles over the years; that's life. Nowhere and nothing is perfect. But on the whole he and we couldn't have been happier.
We decided we wanted the same intimate setting and care for secondary. For that, we've had to pay because, frankly, small secondaries tend to be small because no one wants to go there. Again, best decision we ever made.
You have to let your daughter start school with a positive attitude which I'm sure you will, and try not to be watching for the first time you think they've let you or her down - but keep your options open.
I'm sure she'll have a great time!